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Volatile abundances, coma sources, and ice associations in the nucleus of comet C/2014 Q2 (Lovejoy)

Presentation #210.01 in the session “Comets”.

Published onOct 03, 2021
Volatile abundances, coma sources, and ice associations in the nucleus of comet C/2014 Q2 (Lovejoy)

High-resolution ground-based infrared spectra of bright long-period comet C/2014 Q2 Lovejoy were acquired with NIRSPEC at the Keck Observatory on two post-perihelion dates (UT 2015 February 2 and 3), when the comet was at a heliocentric distance of 1.29 au. H2O was measured simultaneously with CO, CH3OH, H2CO, C2H6, C2H4, C2H2, HCN, and NH3 on both dates and rotational temperatures, production rates, relative abundances, H2O ortho-to-para ratios, and spatial distributions in the coma were determined. The first definitive detection of C2H4 in a comet from ground-based observations is reported. Abundances relative to H2O for all species were found to be in the typical range compared with values for other comets in the overall population to date. There is evidence of variability in rotational temperatures and production rates on time scales that are small compared with the rotational period of the comet. Spatial distributions of volatiles in the coma suggest complex outgassing behavior. CH3OH, HCN, C2H6, and CH4 spatial distributions in the coma are consistent with direct release from associated ices in the nucleus, and are peaked in a more sunward direction compared with co-measured dust. H2O spatial profiles are clearly distinct from CH3OH, HCN, C2H6, and CH4, but this does not rule out a close association of these ices in the nucleus if significant icy grain release in the coma influences H2O spatial distributions. Spatial distributions for C2H2, H2CO, and NH3 suggest extended coma sources in addition to direct release from nucleus ices, providing further evidence for distinct sources and associations of these species in comets compared with other volatiles measured at infrared wavelengths. CO shows a distinct spatial distribution compared with other volatiles, consistent with jet activity from discrete nucleus ice sources.

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